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On a voltage multiplier it stopped working because of too many stages. If I rectified it then used a Marx generator would that work instead? I don't know if a Marx generator will stop working after a certain amount of stages. I could generate the high voltage while using a Tesla coil as well, then rectifying it. All I’m trying to do is create a high voltage DC to charge a very very large capacitor made out of activated carbon.

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    \$\begingroup\$ Isn't 15 kV at 30 mA like 450 Watts? How are you insulating (or planning to insulate) against 1.2 MV? I don't have the first idea how to help you but I am curious about your project. Seems like it might have the potential to induce dielectric breakdown. \$\endgroup\$
    – mkeith
    May 14 at 5:12
  • \$\begingroup\$ Please define your terms: what's an NST? \$\endgroup\$
    – Hearth
    May 14 at 5:13
  • \$\begingroup\$ neon-sign transformer (NST) \$\endgroup\$ May 14 at 5:40
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    \$\begingroup\$ You cannot even think about generating 1.2MV until you have mastered 500 kV. Do you know the 3D E-field gradient stress at that potential? Have you mastered control of partial discharge? Don't even think of doing 500 kV until you have mastered 100 kV safely and reliably.. \$\endgroup\$ May 14 at 5:44
  • \$\begingroup\$ Think and compute the power to drive 1 Gohm leakage at 1GV or even 10 stage 100kV in a pristine clean environment then compare that with the power rating of an NST \$\endgroup\$ May 14 at 6:10

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Beyond about 10:1 the multiplier method gives rapidly diminishing returns with reasonable assumptions. Read a paper on it maybe 25 years ago (Cockcroft-Walton type).

Neon sign transformers have relatively high leakage inductance by design so you can also expect the output voltage to drop quite a bit before you get close to the rated current.

If you don’t mind motors and belts there is always the Van de Graaff generator approach, however an air-insulated generator for 1.2MV would be relatively large, perhaps 3m (10 feet) tall. Compact high voltage equipment requires special techniques such as sulfur hexafluoride dielectric gas- nasty and a very bad greenhouse gas. Your transformer would be used as part of the spray DC power supply at the low potential end.

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  • \$\begingroup\$ C-W multipliers yes are limited by branching of current and continuous leakage, but Marx Gens can have lower air gap leakage but need a reliable trigger to sync all arcs. A motor-driven surface with leather friction is used for static gen ~ 50kV with high power then drives a Marx gen with an NST just for the trigger. \$\endgroup\$ May 14 at 13:30

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